298 HANDBOOK OF NATURE STUDY 



Can you tell why pickerel and bass do not often eat a 

 sunfish ? 



77. The Pickerel. . Lucius lutius. 



MATERIAL: Similar to that for the sunfish. See the report on the 

 fishes of your state. 



Study the structure and color of the pickerel as you did those of 

 the sunfish. Other fishes may be substituted for both of them. 



The pickerel is the tyrant of our lakes and rivers. He 

 attains a length of four feet and will swallow any fish that 

 is not too big for that performance. Pickerel increase and 

 grow very rapidly; one hundred and fifty thousand eggs 

 were found in one. It is fortunate for other fish that most 

 young pickerel are swallowed by larger members of their 

 own kind. 



78. The Crayfish, or Fresh-water Crab. 



MATERIAL : Live crayfish or alcoholic specimens. Observe in the 

 classroom how a crab eats, walks, and swims ; observations at the lake 

 or stream. Remove the large thorax carapace from an alcoholic speci- 

 men and show the branched gills below. Crayfishes must be pro- 

 cured in the fall if this lesson is given in winter. 



The crayfish, or fresh-water crab, is found in nearly all 

 the streams, lakes, and ponds of the United States and Can- 

 ada, but it is probably absent from waters which are very 

 soft, because such waters contain so little lime that the 

 crayfish could not form its hard, outside skeleton, or crust, 

 in them, as for this process lime is necessary. 



Description. The most conspicuous peculiarity of the 

 crayfish is the hard crust, in which its body and limbs are 

 encased. 



The head and the chest are covered by a continuous shield, 

 called the carapace. Behind the thorax we find six well- 

 marked segments, which constitute the abdomen. The tail, 

 which consists of five flaps, is attached to the last abdominal 

 segment. 



